samples/bpf/test_overhead_kprobe_kern.c

   1 /* Copyright (c) 2016 Facebook
   2  *
   3  * This program is free software; you can redistribute it and/or
   4  * modify it under the terms of version 2 of the GNU General Public
   5  * License as published by the Free Software Foundation.
   6  */
   7 #include <linux/version.h>
   8 #include <linux/ptrace.h>
   9 #include <uapi/linux/bpf.h>
  10 #include <bpf/bpf_helpers.h>
  11 #include <bpf/bpf_tracing.h>
  12
  13 #define _(P)                                                                   \
  14         ({                                                                     \
  15                 typeof(P) val = 0;                                             \
  16                 bpf_probe_read_kernel(&val, sizeof(val), &(P));                \
  17                 val;                                                           \
  18         })
  19
  20 SEC("kprobe/__set_task_comm")
  21 int prog(struct pt_regs *ctx)
  22 {
  23         struct signal_struct *signal;
  24         struct task_struct *tsk;
  25         char oldcomm[16] = {};
  26         char newcomm[16] = {};
  27         u16 oom_score_adj;
  28         u32 pid;
  29
  30         tsk = (void *)PT_REGS_PARM1(ctx);
  31
  32         pid = _(tsk->pid);
  33         bpf_probe_read_kernel(oldcomm, sizeof(oldcomm), &tsk->comm);
  34         bpf_probe_read_kernel(newcomm, sizeof(newcomm),
  35                               (void *)PT_REGS_PARM2(ctx));
  36         signal = _(tsk->signal);
  37         oom_score_adj = _(signal->oom_score_adj);
  38         return 0;
  39 }
  40
  41 SEC("kprobe/urandom_read")
  42 int prog2(struct pt_regs *ctx)
  43 {
  44         return 0;
  45 }
  46
  47 char _license[] SEC("license") = "GPL";
  48 u32 _version SEC("version") = LINUX_VERSION_CODE;